DESCRIPTION: Chlorella virus PBCV-1 is the prototype of a unique family of large DNA viruses which infect green algae. The large genomes of these viruses encode a vast repertoire of genes whose predicted products resemble both procaryotic and eucaryotic proteins. The major focus of this renewal proposal is an investigation of Chlorella virus glycosylation. It is thought that PBCV-1 may encode part or all of its own glycosylation machinery, and that this machinery may function not in the ER or Golgi but within viral assembly centers. Thus, the P.I. proposes to identify the genes involved in directing glycosylation, to determine the structure of the oligosacchardie on PBCV-1 glycoproteins, and determine the intracellular site of glycosylation. A second and minor aim of this grant is to pursue the characterization of drug-resistant mutants of Chlorella virus that may contain lesions within the virally encoded DNA topoisomerase II and and mini K+ ion channel. Such mutants could be important in structure-function analyses and in providing an assay for new inhibitors of these proteins, which would bear on treatments for heart disease and cancer.